That doesn't really sound like nute burn....sounds more like a deficiency to me. Nute burn shows as turned down tips and edges of the leaf then the tips and edges will turn yellow and crispy. I have a feeling you are pretty far away from nuteburn.

Here's an excellent link to plant problems....check through and see if you see anything that matches your symptoms.

Revised: The Complete Guide To Sick Plants,pH and Pest Troubles - PlanetGanja.com